The present invention relates generally to devices responsive to angular motion or rotation, and more particularly to an inertial reference device based on the Sagnac interferometer principle for measuring the angular rate of rotation of a platform.
Rotation rate sensors are utilized in a variety of different applications including use as a rate gyroscope and a gyroscope test turntable, as well as application to tachometers for generator speed control, inertial navigation and non-magnetic compasses. In its most common application, the device is disposed in a gimbal mounting and used in the manner of a gyroscope, stabilized about one sensitive axis or about 2 or 3 mutually perpendicular sensitive axes. The device so mounted may provide a space platform stabilized with respect to the system of fixed stars and may be used either for visual aid in navigation or to supply information for actuating automatic piloting or navigating mechanisms, or for remote control of a vehicle. Alternately, the device may be mounted directly upon the frame of a vehicle to supply information in response to the rotation of the vehicle about one or more reference axes. Such information would then be utilized to actuate a computer or other device for automatic or remotely controlled navigation, or like purposes.
It has been known for some time that the Sagnac interferometer can be used to detect the rotation rate of any rotating frame. These interferometers detect rotation rates as small as 15 degree per hour or less.
In essence, the Sagnac interferometer utilizes the principles of general relativity in order to detect angular motion by means of energy circulating in a loop path subjected to angular motion having a component in the plane of the loop. The existence of a measurable effect caused by the angular motion of a given circuit path upon the transmission of electromagnetic waves in the circuit was first verified by experiments performed by G. Sagnac and A. A. Michelson.